Methods for using bi-modal abrasive slurries for mechanical and chemical-mechanical planarization of microelectronic-device substrate assemblies

ABSTRACT

A method and apparatus for making and using slurries for planarizing microelectronic-device substrate assemblies in mechanical and/or chemical-mechanical planarization processes. In one aspect of the invention, a bi-modal slurry is fabricated by removing a first type of selected abrasive particles from a first abrasive particle solution to form a treated flow of the first solution. The treated flow of the first solution is then combined with a flow of a second solution having a plurality of second abrasive particles. The abrasive particles of the first type are accordingly removed from the first solution separately from the second solution such that the second abrasive particles in the second solution do not affect the removal of the abrasive particles of the first type from the first solution. In another aspect of the invention, a second type of selected abrasive particles are removed from the second solution prior to mixing with the first solution. Thus, by combining the treated flow of the first solution with either the treated or untreated flow of the second solution, a single flow of an abrasive slurry is produced having a first distribution of the first abrasive particles about a first mode and a second distribution of the second abrasive particles about a second mode.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.10/155,203, filed May 23, 2002 now U.S. Pat. No. 6,794,289, whichapplication is a continuation of U.S. patent application Ser. No.09/289,790, filed Apr. 9, 1999, which issued as U.S. Pat. No. 6,407,000.

TECHNICAL FIELD

The present invention relates to bi-modal slurries for planarizingmicroelectronic-device substrate assemblies, and to methods andapparatuses for making and using such slurries in mechanical and/orchemical-mechanical planarization processes.

BACKGROUND OF THE INVENTION

Mechanical and chemical-mechanical planarizing processes (collectively“CMP”) are used in the manufacturing of microelectronic devices forforming a flat surface on semiconductor wafers, field emission displaysand many other microelectronic-device substrate assemblies. CMPprocesses generally remove material from a substrate assembly to createa highly planar surface at a precise elevation in the layers of materialon the substrate assembly.

FIG. 1 schematically illustrates an existing web-format planarizingmachine 10 for planarizing a substrate assembly 12. The planarizingmachine 10 has a support table 14 with a top panel 16 at a workstationwhere an operative portion (A) of a polishing pad 40 is positioned. Thetop panel 16 is generally a rigid plate to provide a flat, solid surfaceto support the operative section of the polishing pad 40 duringplanarization.

The planarizing machine 10 also has a plurality of rollers to guide,position and hold the polishing pad 40 over the top panel 16. Therollers include a supply roller 20, first and second idler rollers 21 aand 21 b, first and second guide rollers 22 a and 22 b, and a take-uproller 23. The supply roller 20 carries an unused or preoperativeportion of the polishing pad 40, and the take-up roller 23 carries aused or post-operative portion of the polishing pad 40. Additionally,the first idler roller 21 a and the first guide roller 22 a stretch thepolishing pad 40 over the top panel 16 to hold the polishing pad 40stationary during operation. A drive motor (not shown) drives at leastone of the supply roller 20 and the take-up roller 23 to sequentiallyadvance the polishing pad 40 across the top panel 16. As such, cleanpreoperative sections of the polishing pad 40 may be quickly substitutedfor used sections to provide a consistent surface for planarizing thesubstrate assembly 12.

The web-format planarizing machine 10 also has a carrier assembly 30that controls and protects the substrate assembly 12 duringplanarization. The carrier assembly 30 generally has a carrier head 31with a plurality of vacuum holes 32 to pick up and release the substrateassembly 12 at appropriate stages of the planarizing cycle. A pluralityof nozzles 41 attached to the carrier head 31 dispense a planarizingsolution 42 onto a planarizing surface 43 of the polishing pad 40. Thecarrier assembly 30 also generally has a support gantry 34 carrying adrive assembly 35 that translates along the gantry 34. The driveassembly 35 generally has actuator 36, a drive shaft 37 coupled to theactuator 36, and an arm 38 projecting from the drive shaft 37. The arm38 carries the carrier head 31 via another shaft 39 such that the driveassembly 35 orbits the carrier head 31 about an axis B—B offset from acenter point C—C of the substrate assembly 12.

The polishing pad 40 and the planarizing solution 42 define aplanarizing medium that mechanically and/or chemically-mechanicallyremoves material from the surface of the substrate assembly 12. Theweb-format planarizing machine 10 typically uses a fixed-abrasivepolishing pad having a plurality of abrasive particles fixedly bonded toa suspension material. The planarizing solutions 42 used withfixed-abrasive pads are generally “clean solutions” without abrasiveparticles because the abrasive particles in conventional abrasive CMPslurries may ruin the abrasive surface of fixed-abrasive pads. In otherapplications, the polishing pad 40 may be a nonabrasive pad composed ofa polymeric material (e.g., polyurethane), a resin, or other suitablematerials without abrasive particles. The planarizing solutions 42 usedwith nonabrasive polishing pads are typically “abrasive” CMP slurrieswith abrasive particles.

To planarize the substrate assembly 12 with the planarizing machine 10,the carrier assembly 30 presses the substrate assembly 12 against theplanarizing surface 43 of the polishing pad 40 in the presence of theplanarizing solution 42. The drive assembly 35 then orbits the carrierhead 31 about the offset axis B—B to translate the substrate assembly 12across the planarizing surface 43. As a result, the abrasive particlesand/or the chemicals in the planarizing medium remove material from thesurface of the substrate assembly 12.

CMP processes should consistently and accurately produce a uniformlyplanar surface on the substrate assembly 12 to enable precisefabrication of circuits and photo-patterns. For example, during thefabrication of transistors, contacts, interconnects and othercomponents, many substrate assemblies develop large “step heights” thatcreate a highly topographic surface across the substrate assembly 12. Toenable the fabrication of integrated circuits with high densities ofcomponents, it is necessary to produce a highly planar substrate surfaceat several stages of processing the substrate assembly 12 becausenon-planar substrate surfaces significantly increase the difficulty offorming submicron features. For example, it is difficult to accuratelyfocus photo-patterns to within tolerances of 0.1 μm on nonplanarsubstrate surfaces because submicron photolithographic equipmentgenerally has a very limited depth of field. Thus, CMP processes areoften used to transform a topographical substrate surface into a highlyuniform, planar substrate surface.

In the competitive semiconductor industry, it is also highly desirableto have a high yield of operable devices after CMP processing by quicklyproducing a uniformly planar surface at a desired endpoint on asubstrate assembly. For example, when a conductive layer on thesubstrate assembly 12 is under-planarized in the formation of contactsor interconnects, many of these components may not be electricallyisolated from one another because undesirable portions of the conductivelayer may remain on the substrate assembly 12. Additionally, when asubstrate assembly 12 is over-planarized, components below the desiredendpoint may be damaged or completely destroyed. Thus, to provide a highyield of operable microelectronic devices, CMP processing should quicklyremove material until the desired endpoint is reached.

To accurately create highly planar substrate surfaces at the desiredendpoint, the particle size distribution of planarizing slurries shouldbe consistent from one planarizing cycle to another. One problem withCMP processing, however, is that the abrasive particles may be unstablein the slurry. For example, because many types of abrasive particleshave a large affinity for one another, individual particles in a liquidsolution may agglomerate into larger abrasive elements. The formation ofsuch abrasive elements affects the consistency of the slurry because theextent that the particles agglomerate varies from one batch of slurry toanother, or even within a single batch of slurry as it is delivered tothe planarizing machine. Additionally, large abrasive elements mayscratch the substrate assemblies and produce defects, or they may settleout of the solution. Thus, the agglomeration of abrasive particles is aserious problem for processing substrate assemblies with CMP processing.

One particularly promising CMP slurry being developed by MicronTechnology, Inc. is a liquid solution having a plurality of first andsecond abrasive particles. The first and second abrasive particles aretypically composed of the same material, such as ceria or silica treatedceria abrasive particles. The difference between the first and secondabrasive particles is the size of the particles. This slurry accordinglyhas a “bi-modal” distribution of abrasive particles in which the firstabrasive particles have particles sizes in a first size distributionabout a first mode and the second abrasive particles have particle sizesin a second size distribution about a second mode. In contrast to“singlets ” slurries that have only one mode and a signal sizedistribution of abrasive particles about that mode, bi-modal slurriesare expected to exhibit unusually good polishing rates and planarity onboth topographical and planar substrate surfaces.

Although bi-modal slurries can produce good results, they may fail toachieve consistent results because the abrasive particles are highlyunstable in the solution. The bi-modal slurries mixed by MicronTechnology Inc. from components supplied by Rodel Corporation may evenchange from one planarizing cycle to the next, which greatly increasesthe difficulty in accurately planarizing substrate assemblies. Toresolve the instability of these slurries, a point-of-use filtering maybe performed at the planarizing machine of a single flow of a bi-modalslurry having both the first and second planarizing particles. Filteringthe bi-modal slurry, however, may alter the bi-modal distribution ofabrasive particles to the extent that the bi-modal slurry loses at leastsome of the advantages of using two different particle sizes. Therefore,there is a need for improved bi-modal slurry techniques in CMPprocessing to achieve the potential advantages of such slurries.

SUMMARY OF THE INVENTION

The present invention is directed toward methods and apparatuses formaking and using slurries for planarizing microelectronic-devicesubstrate assemblies in mechanical and/or chemical-mechanicalplanarization processes. In one aspect of the invention, a bi-modalslurry is fabricated by removing a first type of selected abrasiveparticles from a first abrasive particle solution to form a treated flowof the first solution. The treated flow of the first solution is thencombined with a flow of a second solution having a plurality of secondabrasive particles. A single flow of an abrasive slurry thus has a firstdistribution of the first abrasive particles and a second distributionof the second abrasive particles.

In another aspect of the invention, a bi-modal abrasive slurry ismanufactured by also separating a second type of selected abrasiveparticles from the second solution prior to combining the first solutionwith the second solution. Thus, the first and second solutions can betreated independently to avoid affecting the treatment of one solutionby treating the other solution.

In still another aspect of the invention, a planarizing apparatus forplanarizing a substrate assembly in accordance with the inventionincludes a slurry manufacturing assembly, and a dispenser coupled to theslurry manufacturing assembly. The slurry manufacturing assembly caninclude a first feed line for containing the first flow of the firstsolution having the plurality of the first abrasive particles, a secondfeed line for containing the second flow of the second solution havingthe plurality of second abrasive particles, a first filter coupled tothe first feed line to filter the plurality of the first abrasiveparticles separately from the second flow of the second solution, and acombined feed line operatively coupled to the first filter and thesecond feed line for containing a combined flow of the first and secondsolutions after filtering the first solution.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view of a planarizing machine inaccordance with the prior art.

FIG. 2 is a schematic side view of a planarizing system including aplanarizing machine and a slurry manufacturing assembly in accordancewith one embodiment of the invention.

FIG. 3 is a block diagram illustrating first and second slurry solutionsbeing processed according to a method for making a planarizing solutionin accordance with an embodiment of the invention.

FIG. 4 is a bar graph illustrating a slurry made using a slurrymanufacturing assembly and method in accordance with one embodiment ofthe invention having a bi-modal particle size distribution including afirst size distribution of first abrasive particles about a first modeand a second size distribution of smaller second abrasive particlesabout a second mode.

FIG. 5 is a schematic side view of a planarizing system including aplanarizing machine and a slurry manufacturing assembly in accordancewith another embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to methods and apparatuses for makingand using slurries for planarizing microelectronic-device substrateassemblies in mechanical and/or chemical-mechanical planarizationprocesses. Many specific details of certain embodiments of the inventionare set forth in FIGS. 2–5 and the following description to provide athorough understanding of such embodiments. One skilled in the art,however, will understand that the present invention may have additionalembodiments, or that certain embodiments of the invention may bepracticed without several of the details described in the followingdescription.

FIG. 2 is a schematic side view illustrating a planarizing system 100having a planarizing machine 110 and a slurry manufacturing assembly 200in accordance with one embodiment of the invention. The planarizingmachine 110 shown in FIG. 2 is similar to the web-format planarizingmachine 10 described above with reference to FIG. 1, and thus likereference numbers refer to like parts. The planarizing machine 110 canalso be a rotary planarizing machine having a rotating platen and acircular polishing pad, as set forth in U.S. Pat. Nos. 5,645,682 and5,792,709, which are both herein incorporated by reference. Suitableweb-format planarizing machines without the slurry manufacturingassembly 200 are manufactured by Obsidian Corporation. Suitable rotaryplanarizing machines without the slurry manufacturing assembly 200 aremanufactured by Westech Corporation and Strasbaugh Corporation.

The slurry manufacturing assembly 200 generally includes a first supplycontainer 210 containing a first solution 212 and a second supplycontainer 220 containing a second solution 222. In this particularembodiment, the slurry manufacturing assembly 200 also includes a firstparticle removal unit 230 coupled to the first container 210, a secondparticle removal unit 235 coupled to the second container 220, and amixing unit 240 coupled to the first and second particle removal units230 and 235. As explained below, the first and second particle removalunits 230 and 235 are preferably first and second filtration units thatseparately filter selected abrasive particles from the first and secondsolutions 212 and 222. The filtered first and second solutions 212 and222 are then combined in the mixing unit 240 to form an abrasive slurry242 for planarizing the substrate assembly 12 on the planarizing machine110.

The first solution 212 is a first slurry component of the abrasiveslurry 242. The first solution 212 preferably includes water, chemicaladditives (e.g., dispersants, surfactants, oxidants and otheradditives), and a plurality of first abrasive particles 216. The firstabrasive particles 216 can be aluminum oxide particles, ceria particles,silicon dioxide particles, titanium oxide particles, tantalum oxideparticles, ceria treated silica particles, or other suitable abrasiveparticles for removing material from microelectronic device substrateassemblies. The first abrasive particles 216 are preferably the largerparticles of a bi-modal abrasive slurry having particle sizes fromapproximately 0.070–1.0 μm, and more preferably from approximately0.070–0.40 μm. When the first solution 212 is in the first container 210prior to being mixed with the second solution 222, a significantpercentage of the first abrasive particles 216 in the first solution 212may agglomerate to form first particle agglomerations 218. Each firstparticle agglomeration 218 may accordingly include two or moreindividual abrasive particles 216. The individual abrasive particles 216of the first particle agglomerations 218 are generally bonded togetherelectronically, covalently, or by van der walls interaction.

The second solution 222 is accordingly a second component of the mixedslurry 242. The second solution 222 generally includes a liquid 224, thesame additives that are in the first solution 212, and a plurality ofsecond abrasive particles 226. The second abrasive particles 226 canalso be composed of the same material as the first abrasive particles216 in the first solution 212, such as aluminum oxide particles, ceriaparticles, silicon dioxide particles, titanium oxide particles, tantalumoxide particles, ceria treated silica particles, or other suitableabrasive particles for removing material from microelectronic devicesubstrate assemblies. The second abrasive particles 226 are preferablythe smaller particles of a bi-modal abrasive slurry having particlesizes from approximately 0.005–0.20 μm, and more preferably fromapproximately 0.010–0.050 μm. As with the first solution 212, many ofthe abrasive particles 226 in the second solution 222 may agglomerateinto second particle agglomerations 228.

The first particle removal unit 230 of this embodiment is coupled to afirst feed line 219 (indicated by reference numbers 219 a and 219 b)between the first container 210 and the mixing unit 240. The firstparticle removal unit 230 removes a first type of selected abrasiveparticles from the first solution 212. The first particle removal unit230, for example, can have a filter 232 that removes large individualabrasive particles 216 and first particle agglomerations 218 havingsizes greater than a first maximum particle size for the first abrasiveparticles. For example, to create a first particle size distributionfrom approximately 0.070–1.0 μm, the first particle removal unit 230removes first abrasive particles 216 and particle agglomerations 218having sizes greater than 1.0 μm. Similarly, to create a first particlesize distribution from approximately 0.070–0.40 μm, the first particleremoval unit 230 removes first abrasive particles 216 and particleagglomerations 218 having sizes greater than 0.40 μm. Suitable filtersfor removing the first type of selected abrasive particles from thefirst solution 212 are manufactured by Millipore Corporation.

The second particle removal unit 235 of this embodiment is coupled to afeed line 229 (indicated by reference numbers 229 a and 229 b) betweenthe second container 220 and the mixing unit 240. The second particleremoval unit 235 removes a second type of abrasive particles from thesecond solution 222. The second particle removal unit 235 can also havea filter 237 that removes large second abrasive particles 226 and secondparticle agglomerations 228 having sizes greater than a second maximumparticle size. For example, to create a second particle sizedistribution from approximately 0.010–0.20 μm, the second particleremoval unit 235 removes second abrasive particles 226 and particleagglomerations 228 having sizes greater than 0.20 μm. Similarly, tocreate a second particle size distribution from approximately0.010–0.050 μm, the second particle removal unit 235 removes secondabrasive particles 226 and particle agglomerations 228 having sizesgreater than 0.050 μm. Suitable filters for removing the second type ofselected abrasive particles from the second abrasive particles 226 arealso manufactured by Millipore Corporation.

FIG. 3 is a schematic view illustrating the operation of the embodimentof the slurry manufacturing assembly 200 shown in FIG. 2. Referring toFIGS. 2 and 3 together, an untreated flow of the first solution 212initially flows to the first particle removal unit 230 through a firstsegment of the first feed line 219 a, and an untreated flow of thesecond solution 222 initially flows to the second particle removal unit235 through a first segment of the second feed line 229 a. The firstparticle removal unit 230 passes the untreated flow of the firstsolution 212 through the filter 232 to remove large individual firstabrasive particles 216 a and large first particle agglomerations 218from the first solution 212. A treated portion of the first solution 212then passes from the first particle removal unit 230 through a secondsegment of the first feed line 219 b and into the mixing unit 240. Thesecond particle removal unit 235 separately passes the untreated flow ofthe second solution 222 through the filter 237 to remove the largeindividual abrasive particles 226 and second particle agglomerations 228from the untreated second solution 222 to create a treated flow of thesecond solution 222. The second particle removal unit 235 then passesthe treated flow of the second solution 222 through a second segment ofthe second feed line 229 b and into the mixing unit 240.

The mixing unit 240 then mixes the treated first and second solutions212 and 222 together by using an agitator 241, turbulence within aconduit, and/or other suitable devices for adequately mixing the firstand second solutions 212 and 222. The combination of the first andsecond solutions 212 and 222 forms an abrasive slurry 242 with a firstparticle size distribution of larger first abrasive particles 216 abouta first mode and a second particle size distribution of smaller secondabrasive particles 226 about a second mode.

FIG. 4 is a bar graph illustrating a bi-modal particle size distributionof the planarizing slurry 242 having a first particle size distribution280 from approximately 0.20–1.0 μm of the larger first abrasiveparticles 216 (FIG. 2) and a second particle size distribution 290 fromapproximately 0.020–0.20 μm of the smaller second abrasive particles 226(FIG. 2). The first particle size distribution 280 has a first mode 282identifying that a significant percentage of the first abrasiveparticles 216 have particle sizes of approximately 0.3–0.4 μm. Thesecond particle size distribution 290 has a second mode 292 identifyingthat a significant percentage of the second abrasive particles 226 haveparticle sizes of approximately 0.07–014 μm. In another embodiment (notshown), the first particle size distribution is from approximately0.070–0.400 μm with a first mode at approximately 0.250–0.300 μm, andthe second particle size distribution is from approximately 0.010–0.050μm with a second mode at approximately 0.020–0.030 μm.

The embodiment of the slurry manufacturing assembly 200 and the methodof manufacturing the slurry 242 described above with reference to FIGS.2 and 3 are expected to produce bi-modal planarizing slurries withconsistent first and second particle size distributions. One aspect ofthe embodiment of FIGS. 2–4 is the discovery that conventional filteringprocesses for a bi-modal slurry produce inconsistent particle sizedistributions because the filters remove a disproportionate percentageof the larger first abrasive particles after operating for a period oftime. This phenomenon may occur because a common filter sized to removethe upper end of the larger particles is generally too large to alsoremove agglomerations of the smaller particles. Moreover, as the filterbecomes loaded with abrasive particles, the removal rate of largerabrasive particles increases without necessarily increasing the removalrate of the smaller second abrasive particles. The slurry manufacturingsystem 200 and the methods for making the slurry 242 reduce variationsin the first and second particle size distributions because the firstand second solutions 212 and 222 are filtered separately to provide moreconsistent filtering of the individual solutions. The slurrymanufacturing system 200 is accordingly expected to have less loading ofthe filters in a manner that removes a disproportionate percentage ofthe first abrasive particles 216 from the planarizing solution 242.Thus, the manufacturing system 200 and the methods for manufacturing theplanarizing slurry 242 are expected to provide more consistent first andsecond particle size distributions in a bi-modal slurry.

The bi-modal slurry 242 manufactured in accordance with the methoddescribed above with reference to FIGS. 2 and 3 is also expected toproduce good planarizing results. Small abrasive particles are expectedto planarize highly topographic surfaces much faster than large abrasiveparticles. Once the surface of the substrate assembly becomes planar,however, slurries with small particles may have a much slower removalrate than slurries with large particles. The bi-modal planarizingsolution 242 manufactured in accordance with the embodiment of FIGS. 2–4includes the small second abrasive particles 226 to provide selectiveremoval of high areas on the substrate surface at an initial stage of aplanarizing cycle while the substrate surface has topographicalvariations. The bi-modal slurry 242 also includes the larger firstabrasive particles 216 for maintaining a high removal rate once thesubstrate surface becomes planar. The planarizing solution 242accordingly provides selective removal of the topographical features toform a planar surface on the substrate assembly, and then maintains ahigh removal rate of material from the blanket surface to expedientlyplanarize the substrate assemblies.

FIG. 5 is a schematic view illustrating a planarizing system 100 ahaving the planarizing machine 110 and a slurry manufacturing assembly200 a in accordance with another embodiment of the invention. In thisembodiment, the slurry manufacturing assembly 200 a has the first supplycontainer 210 containing the first solution 212, the second supplycontainer 220 containing the second solution 222, and only the firstparticle removal unit 230 coupled to the first container 210 and themixing unit 240. The slurry manufacturing assembly 200 a accordinglyonly treats the flow of the first solution 212 to filter or otherwiseremove the first type of selected abrasive particles from the firstabrasive particles 216. The planarizing system 100 a is otherwiseexpected to operate in a manner similar to the planarizing system 100described above.

Referring to FIG. 2 or FIG. 5, the substrate 12 is planarized byfabricating the mixed slurry 242 and then depositing the mixed slurry242 onto the polishing pad 40 via the nozzles 41 on the carrier head 31.As the mixed slurry 242 covers the polishing pad 40, the carrierassembly 30 presses the substrate 12 against the planarizing surface 43of the pad 40 and translates the substrate 12 across the planarizingsurface 43. Because the slurry manufacturing assemblies 200 and 200 aproduce slurries with consistent first and second particle sizedistributions, the planarizing systems 100 and 100 a are expected toconsistently produce highly planar and substantially defect freesurfaces on the finished substrate assemblies 12.

From the foregoing it will be appreciated that, although specificembodiments of the invention have been described herein for purposes ofillustration, various modifications may be made without deviating fromthe spirit and scope of the invention. Accordingly, the invention is notlimited except as by the appended claims.

1. In the manufacturing of microelectronic devices, a method of planarizing microelectronic-device substrate assemblies, comprising: fabricating an abrasive slurry by filtering a first solution having a plurality of first abrasive particles to create a filtered flow of the first solution, generating a flow of a second solution having a plurality of second abrasive particles separately from filtering the first solution, separating a second type of selected abrasive particles from the second abrasive particles of the second solution to create a filtered flow of the second solution, and combining the filtered flow of the first solution and the filtered flow of the second solution into a single abrasive slurry having a first distribution of the first abrasive particles and a second distribution of the second abrasive particles; dispensing the abrasive slurry onto a planarizing surface of a polishing pad; and removing material from a substrate assembly by pressing the substrate assembly against the planarizing surface and moving at least one of the substrate assembly and the polishing pad with respect to the other to translate the substrate assembly across the planarizing surface.
 2. The method of claim 1 wherein the first abrasive particles have a first size distribution with a first mean and the second abrasive particles have a second size distribution with a second mean smaller than the first mean of the first size distribution, and wherein creating the filtered flow of the fist solution comprises selectively capturing the first type of selected abrasive particles from an untreated flow of the first solution.
 3. The method of claim 1 wherein combining the first solution with the second solution comprises actively agitating the treated first solution and the second solution in a mixing unit.
 4. The method of claim 1 wherein combining the first filtered flow of the first solution with the second filtered flow of the second solution comprises passing the combined filtered first solution and second solution through a turbulent zone of a conduit.
 5. The method of claim 1 wherein combining the filtered flow of the first solution with the filtered flow of the second solution comprises mixing 1–99% by volume of the first filtered solution with 1–99% by volume of the second solution.
 6. The method of claim 5 wherein mixing the first filtered solution with the second filtered solution comprises altering a mix ratio of the first filtered solution and second solution during a single polishing cycle.
 7. The method of claim 6 wherein altering the mix ratio comprises changing from a first mix ratio of the first filtered solution and second filtered solution to a second mix ratio of the first filtered solution and the second solution.
 8. The method of claim 1 wherein the first abrasive particles have a first size distribution with a first mean and the second abrasive particles have a second size distribution with a second mean smaller than the first mean of the first size distribution, and wherein creating the filtered flow of the fist solution comprises filtering an untreated flow of the first solution through a filter that removes first abrasive particles having particle sizes greater than a maximum desired particle size for the first abrasive particles.
 9. The method of claim 8 wherein filtering the first solution comprises passing the first solution through a first filter that removes first abrasive particles from the first solution having particles sizes greater than the maximum desired particle size for the first abrasive particles.
 10. The method of claim 9 wherein passing the first solution through a first filter comprises driving a flow of the first solution through a filter that removes particles having sizes greater than approximately 0.8 μm.
 11. The method of claim 9 wherein passing the first solution through a first filter comprises driving a flow of the first solution through a filter that removes particles having sizes greater than approximately 0.3 μm.
 12. The method of claim 1 wherein the first abrasive particles have a first size distribution with a first mean and the second abrasive particles have a second size distribution with a second mean smaller than the first mean of the first size distribution, and wherein separating a second type of selected abrasive particles from the plurality of the second abrasive particles comprises selectively capturing the second type of selected abrasive particles from an untreated flow of the second solution.
 13. The method of claim 12 wherein the first abrasive particles have a first size distribution with a first mean and the second abrasive particles have a second size distribution with a second mean smaller than the first mean of the first size distribution, and wherein separating a second type of selected abrasive particles from the plurality of the second abrasive particles comprises filtering a flow of the second solution through a filter that removes second abrasive particles having particle sizes greater than a maximum desired particle size for the second abrasive particles.
 14. The method of claim 13 wherein filtering the second solution comprises passing the second solution through a second filter that removes second abrasive particles from the second solution having particles sizes greater than the maximum desired particle size for the second abrasive particles.
 15. The method of claim 14 wherein passing the second solution through a second filter comprises driving a flow of the second solution through a filter that removes particles having sizes greater than approximately 0.15 μm.
 16. The method of claim 14 wherein passing the second solution through a second filter comprises driving a flow of the second solution through a filter that removes particles having sizes greater than 0.050 μm.
 17. In the manufacturing of microelectronic devices, a method of planarizing microelectronic-device substrate assemblies, comprising: fabricating an abrasive slurry by removing a first type of selected abrasive particles from a plurality of first abrasive particles in a first solution to create a treated flow of the first solution, generating a second flow of a second solution having a plurality of second abrasive particles, separating a second type of selected abrasive particles from the second abrasive particles of the second solution to create a treated flow of the second solution, and combining the treated flow of the first solution and the treated flow of the second solution to create a single flow of an abrasive slurry having the first abrasive particles and the second abrasive particles; dispensing the abrasive slurry onto a planarizing surface of a polishing pad; and removing material from a substrate assembly by pressing the substrate assembly against the planarizing surface and moving at least one of the substrate assembly and the polishing pad with respect to the other to translate the substrate assembly across the planarizing surface.
 18. The method of claim 17 wherein the first abrasive particles have a first size distribution with a first mean and the second abrasive particles have a second size distribution with a second mean smaller than the first mean of the first size distribution, and wherein removing the first type of abrasive particles from the plurality of the first abrasive particles comprises selectively capturing the first type of selected abrasive particles from an untreated flow of the first solution.
 19. The method of claim 17 wherein combining the treated flow of the first solution with the treated flow of the second solution comprises actively agitating the treated first solution and the treated second solution in a mixing unit.
 20. The method of claim 17 wherein combining the treated flow of the first solution with the treated flow of the second solution comprises passing the combined treated first solution and treated second solution through a turbulent zone of a conduit.
 21. The method of claim 17 wherein combining the treated flow of the first and second solutions comprises mixing 1–99% by volume of the first solution with 1–99% by volume of the second solution.
 22. The method of claim 21 wherein mixing the treated flow of the first solution with the second solution comprises altering a mix ratio of the first and second solutions during a single polishing cycle.
 23. The method of claim 22 wherein altering the mix ratio comprises changing from a first mix ratio of the treated flow of the first solution and the second solution to a second mix ratio of the first and second solutions.
 24. The method of claim 17 wherein the first abrasive particles have a first size distribution with a first mean and the second abrasive particles have a second size distribution with a second mean smaller than the first mean of the first size distribution, and wherein removing the first type of abrasive particles from the plurality of the first abrasive particles comprises filtering an untreated flow of the first solution through a filter that removes first abrasive particles having particle sizes greater than a maximum desired particle size for the first abrasive particles.
 25. The method of claim 24 wherein filtering the first solution comprises passing the first solution through a first filter that removes first abrasive particles from the first solution having particles sizes greater than the maximum desired particle size for the first abrasive particles.
 26. The method of claim 25 wherein passing the first solution through a first filter comprises driving a flow of the first solution through a filter that removes particles having sizes greater than approximately 0.8 μm.
 27. The method of claim 25 wherein passing the first solution through a first filter comprises driving a flow of the first solution through a filter that removes particles having sizes greater than approximately 0.3 μm.
 28. The method of claim 17 wherein the first abrasive particles have a first size distribution with a first mean and the second abrasive particles have a second size distribution with a second mean smaller than the first mean of the first size distribution, and wherein separating the second type of selected abrasive particles from the plurality of the second abrasive particles comprises selectively capturing the second type of selected abrasive particles from an untreated flow of the second solution.
 29. The method of claim 28 wherein the first abrasive particles have a first size distribution with a first mean and the second abrasive particles have a second size distribution with a second mean smaller than the first mean of the first size distribution, and wherein separating the second type of selected abrasive particles from the plurality of the second abrasive particles comprises filtering a flow of the second solution through a filter that removes second abrasive particles having particle sizes greater than a maximum desired particle size for the second abrasive particles.
 30. The method of claim 29 wherein filtering a flow of the second solution comprises passing the second solution through a second filter that removes second abrasive particles from the second solution having particles sizes greater than the maximum desired particle size for the second abrasive particles.
 31. The method of claim 30 wherein passing the second solution through a second filter comprises driving a flow of the second solution through a filter that removes particles having sizes greater than approximately 0.15 μm.
 32. The method of claim 30 wherein passing the second solution through a second filter comprises driving a flow of the second solution through a filter that removes particles having sizes greater than 0.050 μm. 